I have installed RedHat 7.1 on a PC DELL..
I have installed the packages required by Oracle 12c and I can successfully install Oracle( ./runInstaller) with the graphical interface.
I re-install RedHat 7.1 on the same PC and I update the system, which installs about 500 packages.
I install the packages required required by Oracle 12c and now, I CANNOT install Oracle 12c : on step 5, I have the error :
java.lang No ClassDefFound Error : Could not initialize class java.awt.dnd.DragSource

I have exactly the same problem when using Centos 7.0 instead of Redhat7.1.
It seems to mee that it is a bug in the Java new packages. Maybe, some classes have been renamed or deleted ...
Any idea ?